Hydrocarbon conversion catalyst

ABSTRACT

A hydrocarbon conversion catalyst useful for hydrocracking hydrocarbons to more valuable products comprises one or more hydrogenation components supported on a base containing (1) a crystalline aluminosilicate zeolite having activity for cracking hydrocarbons and (2) a dispersion of silica-alumina in an alumina matrix.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation of application Ser. No. 531,924, filed Sept. 13,1983, now U.S. Pat. No. 4,517,074, which is a divisional of applicationSer. No. 084,761 filed Oct. 15, 1979, and now U.S. Pat. No. 4,419,271.

BACKGROUND OF THE INVENTION

This invention relates to a hydrocracking process and a catalyst for usetherein. More particularly, it relates to a hydrocracking catalyst ofimproved activity, selectivity, and stability for producing middledistillates from heavy gas oils and the like under hydrocrackingconditions.

Petroleum refiners often produce desirable products such as turbinefuel, diesel fuel, and other middle distillate products by hydrocrackinga heavy gas oil, i.e., a hydrocarbon fraction having a boiling pointrange between about 700° F. and 1050° F. Hydrocracking is accomplishedby contacting the heavy gas oil at an elevated temperature and pressurein the presence of hydrogen and a suitable hydrocracking catalyst so asto yield a middle distillate fraction boiling in the 300° to 700° F.range and containing the desired turbine and diesel fuels.

The three main catalytic properties by which the performance of ahydrocracking catalyst for producing middle distillate products isevaluated are activity, selectivity, and stability. Activity may bedetermined by comparing the temperature at which various catalysts mustbe utilized under otherwise constant hydrocracking conditions with thesame feedstock so as to produce a given percentage (usually 60%) ofproducts boiling below 700° F. The lower the activity temperature for agiven catalyst, the more active such a catalyst is in relation to acatalyst of higher activity temperature. Selectivity of hydrocrackingcatalysts may be determined during the foregoing described activity testand is measured as that percentage fraction of the 700° F.-minus productboiling in the range of middle distillate or midbarrel products, i.e.,300° to 700° F. Stability is a measure of how well a catalyst maintainsits activity over an extended time period when treating a givenhydrocarbon feedstock under the conditions of the activity test.Stability is generally measured in terms of the change in temperaturerequired per day to maintain a 60% or other given conversion.

As could be expected, the aim of the ait is to provide a catalyst havingat once the highest possible activity, selectivity, and stability.Catalysts usually utilized for hydrocracking comprise a Group VIII metalcomponent, most often cobalt or nickel sulfides, in combination with aGroup VIB metal component, most often molybdenum or tungsten sulfides,supported on a refractory oxide. For given proportions of Group VIII andGroup VIB metal components, the activity, selectivity, and stability ofa catalyst change dramatically with different supports. Supportmaterials comprising crystalline aluminosilicate zeolites, such asZeolite Y in the hydrogen form, generally provide high activity but lowselectivity, whereas support materials consisting essentially ofrefractory oxides, such as alumina, magnesia, and silica-alumina,generally have relatively poor activity but high selectivity.

The object of the present invention, therefore, is to provide ahydrocracking catalyst having superior overall catalytic properties forhydrocracking hydrocarbons. More specifically, it is an object of theinvention to provide a catalyst having superior overall activity,selectivity, and stability for hydrocracking in comparison to prior artcatalysts. It is a further object to provide a hydrocracking process forconverting gas oils and the like to middle distillate products. It is afurther object to provide a support or carrier material useful with ahydrogenation component as a catalyst for hydrogenating and/orhydrocracking hydrocarbons. These and other objects and advantages willbecome more apparent in light of the following description of theinvention.

SUMMARY OF THE INVENTION

The present invention is an improvement of the catalyst described inU.S. Pat. No. 4,097,365, herein incorporated by reference. The catalystdescribed in this reference is a mid-barrel hydrocracking catalystcomprising hydrogenation components on a refractory oxide supportcomprising silica-alumina dispersed in a matrix of alumina. The presentinvention improves this catalyst by including in the support acrystalline alumino-silicate zeolite having cracking activity, such ashydrogen Y zeolite or a rare earth-exchanged Y zeolite. In addition tohaving excellent activity for hydrodenitrogenation andhydrodesulfurization, the catalyst of the invention has been found tohave superior overall properties of activity, selectivity, and stabilityfor hydrocracking in comparison to the catalyst described in U.S. Pat.No. 4,097,365. In the usual instance, the catalyst of the invention ismore active, more stable, and more selective than comparison catalystshaving supports consisting essentially of either a dispersion ofsilica-alumina in an alumina matrix or a zeolite plus a refractory oxideother than a dispersion of silica-alumina in an alumina matrix.

In its broadest embodiment, the present invention provides a catalystsupport comprising in intimate admixture (1) a crystallinealuminosilicate zeolite having cracking activity and (2) a dispersion ofsilica-alumina in an alumina matrix. Although the support is mostpreferred when used in conjunction with a hydrogenation component, itmay itself be utilized in the absence of a hydrogenation component as acatalyst for converting hydrocarbons to more valuable products by acidcatalyzed reactions, such as catalytic cracking, isomerization ofn-paraffins to isoparaffins, isomerization of alkyl aromatics,alkylation, and transalkylation of alkyl aromatics.

DETAILED DESCRIPTION OF THE INVENTION

The catalyst of the invention is an intimate composite of one or morehydrogenation components, a crystalline aluminosilicate zeolite havingcatalytic activity for cracking hydrocarbons, and a dispersion ofsilica-alumina in a matrix consisting essentially of alumina. Thehydrogenation components useful in the invention are the metals, oxides,and sulfides of uranium, the Group VIII elements, and the Group VIBelements. The most suitable hydrogenation components are selected fromthe group consisting of the metals, oxides, and sulfides of platinum,palladium, cobalt, nickel, tungsten, and molybdenum. The preferredcatalyst contains at least one Group VIII metal component, and at leastone Group VIB metal component, with the most preferred combination beinga nickel and/or cobalt component with a molybdenum and/or tungstencomponent.

The hydrogenation component or components are intimately composited on abase or support comprising a mixture of one or more crystallinealuminosilicate zeolites having cracking activity and a heterogeneousdispersion of finely divided silica-alumina in a matrix of alumina. Thesuitable zeolites for use herein include crystalline aluminosilicatemolecular sieves having catalytic activity for cracking hydrocarbons.Many naturally-occurring and synthetic crystalline aluminosilicatezeolites known in the art are useful in the invention, including, forexample, faujasite, mordenite, erionite, Zeolite Y, Zeolite X, ZeoliteL, Zeolite Omega, Zeolite ZSM-4, and their modifications. These andother such zeolitic molecular sieves are known to have activity forcracking hydrocarbons when a substantial proportion of the ion exchangesites are occupied with hydrogen ions or multivalent metal-containingcations, particularly rare earth cations. Normally, crystallinealuminosilicate zeolites are obtained in the alkali metal form and assuch are largely inactive for catalytically cracking hydrocarbons. Toproduce a zeolite having cracking activity, the alkali metals areusually replaced with multivalent metal-containing cations, hydrogenions, or hydrogen ion precursors (e.g. ammonium ion). This replacementof cations is generally accomplished by ion exchange, a methodwell-known in the art wherein the zeolite in the sodium or other alkalimetal form is contacted with an aqueous solution containing hydrogenions, ammonium ions, rare earth ions, or other suitable cations.Replacing even a portion of the sodium ions produces a zeolite havingsome cracking activity, but reducing the alkali metal content to lessthan 5 wt.%, preferably to less than 1 wt.%, and most preferably to lessthan about 0.5 wt.% (calculated as the alkali metal oxides), results ina material having substantial cracking activity, with the activityvarying according to the zeolite and the amount of alkali metalsremoved.

In addition to the zeolites referred to above, many other crystallinealuminosilicate zeolites in their non-alkali metal forms may be utilizedin the catalyst support of the invention. Preferred zeolites contain atleast 50% of their pore volume in pores of diameter greater than 8Angstroms, with Zeolite Y (and its modifications) in the hydrogen formor in other forms imparting cracking activity to the zeolite beingpreferred zeolites for use in the invention. Also preferred are zeolitesthat have been ion-exchanged with ammonium ions and then steamstabilized in accordance with the teachings of U.S. Pat. No. 3,929,672,herein incorporated by reference. The most highly preferred zeolite is amaterial known as LZ-10, a zeolitic molecular sieve available from UnionCarbide, Linde Division. Although LZ-10 is a proprietary material, it isknown that LZ-10 is a modified Y zeolite having a silica to aluminaratio between about 3.5 and 6.0, a surface area between about 500 and700 m² /gm, a unit cell size between about 24.25 and 24.35 Angstroms,water absorption capacity less than about 8% by weight of the zeolite(at 4.6 mm partial pressure of water vapor and 25° C.), and anion-exchange capacity less than 20% of that of a sodium Y zeolite ofcomparable silica to alumina ratio. When used as a hydrocrackingcatalyst, LZ-10 is highly active and selective for midbarrelhydrocracking, especially when composited with alumina and suitablehydrogenation components.

The support material utilized in the invention usually comprises between2 and about 80% by weight, preferably between about 10 and about 70% byweight, of a crystalline aluminosilicate zeolite such as LZ-10. Thesupport also comprises a substantial proportion of a heterogeneousdispersion of finely divided silica-alumina in an alumina matrix.Usually, the dispersion comprises at least 15% by weight of the support,with the preferred and most preferred proportions being in therespective ranges of 30 to 98% and 30 to 90% by weight of the support.

One convenient method of preparing the catalyst support herein is tocomull an alumina hydrogel with a silica-alumina cogel in hydrous or dryform. The cogel is preferably homogeneous and may be prepared in amanner such as that described in U.S. Pat. No. 3,210,294. Alternatively,the alumina hydrogel may be comulled with a "graft copolymer" of silicaand alumina that has been prepared, for example, by first impregnating asilica hydrogel with an alumina salt and then precipitating alumina gelin the pores of the silica hydrogel by contact with ammonium hydroxide.In the usual case, the cogel or copolymer (either of which usuallycomprises silica in a proportion by dry weight of 20 to 96%, preferably50 to 90%) is mulled with the alumina hydrogel such that the cogel orcopolymer comprises 5 to 75% by weight, preferably 20 to 65% by weight,of the mixture. The overall silica content of the resulting dispersionon a dry basis is usually between 1 and 75 wt.%, preferably between 5and 45 wt.%.

The mulled mixture of alumina gel with either a silica-alumina cogel ora silica and alumina "graft copolymer" may be utilized in the gel formor may be dried and/or calcined prior to combination with the zeolite.In the preferred method of preparation, the cogel or copolymer is spraydried and then crushed to a powdered form, following which the powder ismulled with a zeolite powder containing hydrogen ions, hydrogen ionprecursors, or multivalent metal-containing cations, the amounts ofcogel or copolymer mulled with said zeolite being such that the supportwill ultimately contain zeolite and dispersion in the proportions setforth hereinbefore. If desired, a binder may also be incorporated intothe mulling mixture, as also may one or more active metal hydrogenationcomponents in forms such as ammonium heptamolybdate, nickel nitrate orchloride, ammonium metatungstate, cobalt nitrate or chloride, etc. Aftermulling, the mixture is extruded through a die having suitable openingstherein, such as circular openings of diameters between about 1/32 and1/8 inch. Preferably, however, the die has openings therein in the shapeof three-leaf clovers so as to produce an extrudate material similar tothat shown in FIGS. 8 and 8A of U.S. Pat. No. 4,028,227. The extrudedmaterial is cut into lengths of about 1/32 to 3/4 inch, preferably 1/4to 1/2 inch, dried, and calcined at an elevated temperature.

If desired, hydrogenation components may be composited with the supportby impregnation; that is, rather than comulling the hydrogenationcomponents with the support materials, the zeolite and dispersion aremulled, extruded, cut into appropriate lengths, and calcined. Theresulting particles are then contacted with one or more solutionscontaining the desired hydrogenation components in dissolved form, andthe composite particles thus prepared are dried and calcined to producefinished catalyst particles.

Usually, the finished catalyst contains at least about 0.5 wt.% ofhydrogenation components, calculated as the metals. In the usualinstance, wherein a Group VIII metal and a Group VIB metal component areutilized in combination, the finished catalyst contains between about 5%and 35%, preferably between about 10 and 30% by weight, calculated asthe respective trioxides, of the Group VIB metal components and betweenabout 2% and 15%, preferably between 3 and 10% by weight, calculated asthe respective monoxides, of the Group VIII metal components.

If desired, a phosphorus component may also be incorporated in thecatalyst by either comulling the support materials with phosphoric acidor including phosphoric acid in the impregnating solution. Usual andpreferred proportions of phosphorus in the catalyst fall in the rangesof 1 to 10 wt.% and 3 to 8 wt.%, calculated as P₂ O₅.

The hydrogenation components, which will largely be present in theiroxide forms after calcination in air, may be converted to their sulfideforms, if desired, by contact at elevated temperatures with a reducingatmosphere comprising hydrogen sulfide. More conveniently, the catalystis sulfided in situ, i.e., by contact with a sulfur-containing feedstockto be catalytically converted to more valuable hydrocarbons in suchprocesses as hydrocracking, hydrotreating, etc.

The foregoing described catalysts are especially useful forhydrogenation reactions, such as hydrodenitrogenating andhydrodesulfurizing hydrocarbons, but are particularly useful withrespect to hydrocracking to convert a hydrocarbon feedstock to a morevaluable product of lower average boiling point and lower averagemolecular weight. The feedstocks that may be treated herein byhydrogenation include all mineral oils and synthetic oils (e.g., shaleoil, tar sand products, etc.) and fractions thereof. Typical feedstocksinclude straight run gas oils, vacuum gas oils, deasphalted vacuum andatmospheric residua, coker distillates, and catcracker distillates.Preferred hydrocracking feedstocks include gas oils and otherhydrocarbon fractions having at least 50% by weight of their componentsboiling above 700° F. Suitable and preferred conditions forhydrocracking gas oil feedstocks, as well as for hydrodenitrogenatingand/or hydrodesulfurizing such feedstocks, are:

                  TABLE I                                                         ______________________________________                                                       Suitable                                                                              Preferred                                              ______________________________________                                        Temperature, °F.                                                                        500-850   600-800                                            Pressure, psig    750-3500 1000-3000                                          LHSV             0.3-5.0   0.5-3.0                                            H.sub.2 /Oil, MSCF/bbl                                                                          1-10     2-8                                                ______________________________________                                    

As will be shown by the following Examples, which are provided forillustrative purposes and are not to be construed as limiting the scopeof the invention as defined by the claims, the present catalysts havebeen found to possess superior overall catalytic properties with respectto activity, selectivity, and stability when conversion of gas oils tomidbarrel products by hydrocracking is desired. In many instances, thecatalysts of the invention have been found to be superior in each of thethree main performance categories of activity, selectivity, andstability.

EXAMPLE I

An experiment was performed to compare the activity, selectivity, andstability of catalysts of the invention containing LZ-10 and adispersion of silica alumina in a gamma alumina matrix versus catalystshaving supports consisting essentially of LZ-10 and gamma alumina.Following are the preparation procedures used for Catalyst Nos. 1through 4, with Catalyst Nos. 2 and 3 being representative of theinvention and Catalyst Nos. 1 and 4 being the comparison catalysts.

Catalyst No. 1

A mixture of 10% by weight powdered LZ-10 that had been ion-exchangedwith ammonium nitrate to reduce the sodium content to about 0.1% byweight sodium (as Na₂ O) and 90% by weight gamma alumina was extrudedthrough a die having openings therein in a three-leaf clover shape, eachleaf being defined by about a 270° arc of a circle having a diameterbetween about 0.02 and 0.04 inches. The extruded material was cut ino1/4-1/2 inch lengths and calcined at 900° F. in air to convert the LZ-10material to the hydrogen form. The calcined particles (300 gm) were thenimpregnated with 330 ml of an aqueous solution containing 67 gm ofnickel nitrate (Ni(NO₃)₂. 6H₂ O) and 108 gm of ammonium metatungstate(91% WO₃ by weight). After removing excess liquid, the catalyst wasdried at 230° F. and calcined at 900° F. in flowing air. The finalcatalyst contained 4.4 wt.% nickel components (calculated as NiO) and25.0 wt.% tungsten components (calculated as WO₃).

Catalyst No. 2

The procedure described for Catalyst No. 1 was repeated except that inplace of alumina a dispersion of spray dried, powdered silica-alumina inalumina prepared in a manner similar to that of Example 3 of U.S. Pat.No. 4,097,365 was used. The dispersion was prepared by mixing 44 partsby dry weight of a 75/25 silica-alumina graft copolymer and 56 parts byweight of hydrous alumina gel. In the final catalyst, the supportconsisted essentially of 10% LZ-10 in the hydrogen form and 90%dispersion of silica alumina in an alumina matrix, the dispersionconsisting overall of 33% by weight silica and 67% by weight alumina.The resulting catalyst contained 4.1% by weight nickel components (asNiO) and 24.2% by weight tungsten components (as WO₃).

Catalyst No. 3

This catalyst was prepared in the same manner as Catalyst No. 2 exceptthat the proportions of LZ-10 and dispersion admixed to prepare thesupport were adjusted so that in the final catalyst the proportion ofLZ-10 in the support was 5% by weight and that of the dispersion, 95% byweight. The final catalyst contained 4.1% by weight nickel components(as NiO) and 23.6% by weight tungsten components (as WO₃) on a supportof 5% LZ-10 and 95% dispersion.

Catalyst No. 4

This catalyst was prepared in the same manner as Catalyst No. 1 exceptthat the proportions of LZ-10 and alumina admixed during preparationwere such that in the final catalyst the proportion of LZ-10 in thesupport was 20% by weight and that of the gamma alumina, 80% by weight.The final catalyst contained 4.1% by weight nickel components (as NiO)and 24.4% by weight tungsten components (as WO₃) on a support of 20%LZ-10 and 80% gamma alumina.

Each of the foregoing catalysts was then activity tested according tothe following method. A preheated light Arabian vacuum gas oil havingthe chemical and physical properties shown in Table II was passed on aonce-through basis through an isothermal reactor containing 140 ml ofcatalyst particles uniformly mixed with 160 ml of 10 to 20 mesh quartz.Operating conditions were as follows: 1.0 LHSV, 2000 psig, aonce-through hydrogen flow of 10,000 scf/bbl, and a run length ofapproximately 10 days. The temperature of the reactor was adjusted toprovide a 60 volume percent conversion to products boiling at 700° F. orless. The results of the activity testing are reported in Table III.

                                      TABLE II                                    __________________________________________________________________________    PROPERTIES OF LIGHT ARABIAN VACUUM GAS OIL                                    __________________________________________________________________________    Gravity, °API                                                                      22.3  Pour Point, °F.                                                                       100.0                                        Distillation, °F., D-1160                                                                Sulfur, XRF, wt. %                                                                           2.37                                         IBP/5       693/760                                                                             Nitrogen, KJEL, wt. %                                                                        0.079                                        10/20       777/799                                                                             Hydrogen, wt. %                                                                              12.20                                        30/40       815/832                                                                             Chlorine, ppm  <1.0                                         50/60       850/870                                                                             Carbon Residue, D-189, wt. %                                                                 0.14                                         70/80       894/920                                                                             Viscosity, SSU at 100° F.                                                             319.0                                        90/95       958/979                                                                             Viscosity, SSU at 210° F.                                                             51.1                                         EP/% Rec.   1053/99.0                                                                           Specific Gravity                                                                             0.9200                                       __________________________________________________________________________

                                      TABLE III                                   __________________________________________________________________________       Catalyst    Activity.sup.1                                                                          Selectivity.sup.2                                       Description Reactor Temp. to                                                                        Vol. % Conv. to                                                                          Stability.sup.3                           No.                                                                              of Support  Provide 60% Conv.                                                                       300°-700° F. Product                                                       °F./day                            __________________________________________________________________________    1  10% LZ-10 and                                                                             772° F.                                                                          83.5       0.68                                         90% Gamma Alumina                                                          2  10% LZ-10 and                                                                             750° F.                                                                          83.5       -0.72                                        90% SiO.sub.2 --Al.sub.2 O.sub.3 in                                           Gamma Alumina Matrix                                                       3  5% LZ-10 and                                                                              776° F.                                                                          87.4       0.09                                         95% SiO.sub.2 --Al.sub.2 O.sub.3 in                                           Gamma Alumina Matrix                                                       4  20% LZ-10 and                                                                             750° F.                                                                          75.2       0.39                                         80% Gamma Alumina                                                          __________________________________________________________________________     .sup.1 Activity data are those obtained on tenth day of run.                  .sup.2 Selectivity data are an average of data obtained over 10 days and      are calculated as the volume of 300°-700° F. components to      the total volume of components boiling at or below 700° F.             .sup.3 Stability data were calculated using the reactor temperature           required to produce a 60% conversion on the 2nd and 10th days of the run.

The data in Table III reveal that in comparison to the two hydrocrackingcatalysts having supports consisting of LZ-10 and gamma alumina, thecatalysts of the invention are far superior in terms of overallactivity, selectivity, and stability. A comparison of Catalyst Nos. 1and 2 shows that, for the same percentage of LZ-10 in the support,Catalyst No. 2 prepared in accordance with the invention was 22° F. moreactive and much more stable than Catalyst No. 1. In addition, CatalystNo. 2 proved to be as selective for producing midbarrel products asCatalyst No. 1. Comparing Catalysts Nos. 2 and 4 and Catalysts 3 and 1shows that the catalysts of the invention are as active, butsubstantially more stable and selective, than their LZ-10-aluminacomparisons containing twice as much zeolite.

EXAMPLE II

A second experiment was performed under the run conditions of Example Ito demonstrate the improved performance attainable with the catalysts ofthe invention in comparison to the catalysts described in U.S. Pat. No.4,097,365. The catalysts utilized in the experiment were prepared asfollows:

Catalyst No. 5

A catalyst support was prepared in the same manner as described inExample 3 of U.S. Pat. No. 4,097,365 except that 54 parts of thesilica-alumina graft copolymer were mixed with 46 parts of the hydrousalumina gel. The support (in the size and shape as Catalyst No. 1) wascalcined and impregnated with a nickel nitrate-ammonium metatungstatesolution as in the preparation of Catalyst No. 1, and then dried andcalcined in the same way. The final catalyst contained 4.1 wt.% nickelcomponents (as NiO) and 24.4 wt.% tungsten components (as WO₃) supportedon a base consisting essentially of a dispersion of 75/25 silica-aluminain an alumina matrix, the base having an overall silica content of 40%and an overall alumina content of 60%.

Catalyst No. 6

This catalyst was prepared in the same manner as Catalyst No. 5 exceptthat LZ-10 in the ammonium form and peptized alumina binder wereincorporated into the support such that, after calcination, LZ-10 in thehydrogen form comprised 10 percent by weight of the support and thebinder comprised 20 percent by weight of the support.

The results obtained from testing Catalysts Nos. 5 and 6 for activity,selectivity, and stability are reported in Table IV.

                                      TABLE IV                                    __________________________________________________________________________       Catalyst Activity.sup.1                                                                          Selectivity.sup.2                                          Description                                                                            Reactor Temp. to                                                                        Vol. % Conv. to                                                                          Stability.sup.3                              No.                                                                              of Support                                                                             Provide 60% Conv.                                                                       300°-700° F. Product                                                       °F./day                               __________________________________________________________________________    5  Dispersion of                                                                          773° F.                                                                          88.7       0.23                                            SiO.sub.2 /Al.sub.2 O.sub.3 in                                                Gamma Alumina                                                                 Matrix                                                                     6  10% LZ-10 and                                                                          753° F.                                                                          87.4       0.05                                            90% Dispersion                                                                of SiO.sub.2 --Al.sub.2 O.sub.3 in                                            Gamma Alumina                                                              __________________________________________________________________________     .sup.1 Activity data are those obtained on tenth day of run.                  .sup.2 Selectivity data are an average of data obtained over 10 days and      are calculated as the volume of 300°-700° F. components to      the total volume of components boiling at or below 700° F.             .sup.3 Stability data were calculated using the reactor temperatures          required to produce a 60% conversion on the 2nd and 10th days of the run.

As is self-evident from the data in Table IV, the catalyst of theinvention, Catalyst No. 6, proved far superior to a catalyst similar tothat described in Example 3 of U.S. Pat. No. 4,097,365. Catalyst No. 6provides substantially more activity and stability than Catalyst No. 5with no significant loss in selectivity.

EXAMPLE III

A third comparison experiment was run to determine the activity of twocatalysts of the invention comprising nickel and molybdenum componentson supports comprising LZ-10 and a dispersion of silica-alumina in agamma alumina matrix versus a catalyst comprising nickel and molybdenumcomponents on a support comprising LZ-10 and alumina but containing nodispersion. The catalysts were prepared as follows:

Catalyst No. 7

Sixty grams of gamma alumina powder were comulled with 120 gm LZ-10 inthe ammonia form, 20 gm peptized alumina, 75 gm ammonium heptamolybdate((NH₄)₆ Mo₇ O₂₄.4H₂ O), and 85 gm nickel nitrate hexahydrate. The mulledmixture was extruded through a die similar to that used in preparingCatalyst No. 1, cut into 1/4-1/2 inch lengths, and calcined in air at900° F. The resulting catalyst contained 7.7 wt.% nickel components (asNiO), 21.9 wt.% molybdenum components )as MoO₃), about 43 wt.% LZ-10,about 21 wt.% gamma alumina, and the remainder (about 7 wt.%) peptizedalumina.

Catalyst No. 8

This catalyst was prepared in the same fashion as was Catalyst No. 7except that, in place of the gamma alumina, 60 gm of a powdereddispersion of 75/25 silica-alumina in a gamma alumina matrix was used.The dispersion was prepared by spray drying a mixture comprising 33parts by weight silica-alumina graft copolymer with 67 parts by weightof hydrous alumina gel. The final catalyst contained 7.4 wt.% nickelcomponents (as NiO), 21.5 wt.% molybdenum components (as MoO₃), about 43wt.% LZ-10, about 7% of peptized alumina, and about 21% of thedispersion containing 25 wt.% silica and 75 wt.% alumina overall.

Catalyst No. 9

This catalyst was prepared in the same manner as Catalyst No. 8 exceptthat the dispersion was prepared by mixing 54 parts by weight of 75/25silica-alumina graft copolymer with 46 parts by weight of hydrousalumina gel. The final catalyst was of the same composition as CatalystNo. 8 except for the overall silica and alumina contents of thedispersion, which were 40% and 60% by weight, respectively.

The foregoing catalysts were subjected to the 10-day activity testsdescribed in Example I, and the results are shown in Table V. As shown,the results prove the superiority of the catalysts of the invention(i.e., Catalysts Nos. 8 and 9) in all categories. In addition, the datashow the improvement obtained when the silica contents of the catalystsof the invention are increased.

                                      TABLE V                                     __________________________________________________________________________       Catalyst    Activity.sup.1                                                                          Selectivity.sup.2                                       Description Reactor Temp. To                                                                        Vol. % Conv. to                                                                          Stability.sup.3                           No.                                                                              of Support  Provide 60% Conv.                                                                       300°-700° F. Product                                                       °F./day                            __________________________________________________________________________    7  LZ-10 and   745° F.                                                                          74.8       1.43                                         Gamma Alumina                                                              8  LZ-10 and   743° F.                                                                          79.4       0.17                                         SiO.sub.2 --Al.sub.2 O.sub.3 in Gamma                                         Alumina Matrix                                                                (25% SiO.sub.2 Overall)                                                    9  LZ-10 and SiO.sub.2 --                                                                    733° F.                                                                          79.5       0.88                                         Al.sub.2 O.sub.3 in Gamma                                                     Alumina Matrix                                                                (40% SiO.sub.2 Overall)                                                    __________________________________________________________________________     .sup.1 Activity data are those obtained on tenth day of run.                  .sup.2 Selectivity data are an average of data obtained over 10 days and      are calculated as the volume of 300°-700° F. components to      the total volume of components boiling at or below 700° F.             .sup.3 Stability data were calculated using the reactor temperatures          required to produce a 60% conversion on the 2nd and 10th days of the run.

EXAMPLE IV

A fourth experiment was conducted to compare the catalytic properties ofa catalyst of the invention incorporating a stabilized Y zeolite withthe catalytic properties of a similar catalyst containing stabilized Yzeolite but containing no dispersion of silica-alumina in an aluminamatrix. The two catalysts were prepared as follows:

Catalyst No. 10

A mixture of 40 gm stabilized Y zeolite (prepared in accordance with themethod described in U.S. Pat. No. 3,929,672 for Catalyst A in Example 16but without adding palladium), 40 gm peptized alumina binder, and 120 gmof dispersion of the kind described for Catalyst No. 9 were comulledwith a 380 ml aqueous solution containing 78 gm ammonium heptamolybdatetetrahydrate, 29.1 gm phosphoric acid (85% H₃ PO₄), and 85 gm nickelnitrate hexahydrate. The resulting material was extruded in the samemanner as Catalyst No. 1, cut into particles of 1/4-1/2 inch length, andcalcined in air at 900° F. The final catalyst contained about 6 wt.%nickel components (as NiO), about 19 wt.% molybdenum components (asMoO₃), and about 6 wt.% phosphorus components (as P₂ O₅).

Catalyst No. 11

This catalyst was prepared in a manner similar to that of Catalyst No.10 with the major difference being (1) that the comulled mixture wasextruded through a die having circular openings therein of about 1/16inch diameter and (2) the comulled mixture contained 120 gm of powderedgamma alumina instead of the dispersion. The resulting catalyst had thesame percentage composition of nickel, molybdenum, and phosphoruscomponents as Catalyst No. 10.

The foregoing catalysts were then tested in a manner similar to thatdescribed in Example I except that Catalyst No. 10 was run for 13.6 daysand Catalyst No. 11 for 8 days. The data obtained are presented in TableVI.

                                      TABLE VI                                    __________________________________________________________________________                 Activity.sup.1                                                                        Selectivity.sup.2                                           Catalyst  Reactor Temp.                                                                         Vol. % Conv. To                                             Description                                                                             To Provide                                                                            300°-700° F.                                                               Stability.sup.3                               No.                                                                              of Support                                                                              60% Conv.                                                                             Product    °F./Day                                __________________________________________________________________________    10 Stabilized Y plus                                                                       733° F.                                                                        70.0       1.1 (days                                        SiO.sub.2 --Al.sub.2 O.sub.3 in                                                                            3.2 to 10)                                       Gamma Alumina                0 (days 10.9                                     Matrix                       to 13.6)                                      11 Stabilized Y plus                                                                       739° F.                                                                        73.0       0.58 (days                                       Gamma Alumina                2.8 to 8.1)                                   __________________________________________________________________________     .sup.1 Activity as reported for Catalyst No. 10 is a corrected value          obtained from data determined for the 10th day of the run, and the            activity data reported for Catalyst No. 11 are extrapolated from data         derived on the eighth day of the run.                                         .sup.2 Selectivity data are the average of data obtained during first 10      days with Catalyst No. 10 and the 8 days of run with Catalyst No. 11.         .sup.3 Stability data were calculated using the reactor temperatures          required to produce a 60% conversion on the days specified in the Table. 

The results in Table VI again show the overall superiority of thecatalyst of the invention (Catalyst No. 10) with respect to activity,selectivity, and stability. The 6° F. differential in activity betweenthe catalyst of the invention and the comparison catalyst representsabout a 20% improvement in activity. Especially significant is the factthat after 10.9 days, Catalyst No. 10 showed no signs of deactivation,and thus the high activity indicated by the 733° F. result could beexpected to be maintained.

EXAMPLE V

Catalyst No. 12 was prepared in the same manner as Catalyst No. 9 exceptthat LZ-20 rather than LZ-10 was utilized. (LZ-20 is a crystallinealuminosilicate zeolite, available from Union Carbide, Linde Division,having a unit cell size, a water sorption capacity, a surface area, andan ion exchange capacity somewhat higher than that of LZ-10.) Thecatalyst was tested in the same manner as described in Example I exceptthat the run length was 8.5 days rather than 10 days. The resuts of theexperiment were as follows: Activity: 733° F. (the operating temperatureon the last day of run), Selectivity: 67.0% (as the average percentageconversion to middle distillates during the run), and Stability: 1.94°F./day as calculated between 2.1 days and the end of run and 1.86°F./day between 5.3 days and end of the run. A comparison of these datawith those of Catalyst No. 9 in Example III indicate that better resultsare obtained with LZ-10 in the catalyst support of the invention thanwith LZ-20.

EXAMPLE VI

Catalyst No. 13 was prepared by mulling a mixture consisting essentiallyof 140 gm of a dispersion of silica-alumina in an alumina matrix as wasused to prepare Catalyst No. 5, 20 gm LZ-10 in ammonia form (i.e., as inExample I), and 40 gm peptized alumina with 380 ml of an aqueoussolution containing 78 gm ammonium heptamolybdate tetrahydrate, 29.1 gmphosphoric acid (85% H₃ PO₄), and 85 gm nickel nitrate hexahydrate. Themulled mixture was wet sufficiently to form a paste and extruded througha die similar to that described in Example I. The extrudate was cut into1/4-1/2 inch particles in length, dried, and calcined at 900° F. Thefinished catalyst contained 7.6 wt.% nickel components (as NiO), 21.2wt.% molybdenum components (as MoO₃), and 7.1 wt.% phosphorus components(as P₂ O₅).

The foregoing catalyst was tested for its catalytic properties in thesame manner as described in Example I, and the results were as follows:Activity: 750° F. on the tenth day of run, Selectivity: 85.6 as theaverage over the ten days of operation, and Stability: 0.85° F./day fromdays 2 through 10 and 0.11° F./day from days 5.8 through 10. Theseresults indicate the high activity, selectivity, and stability of thisembodiment of the catalyst of the invention.

EXAMPLE VII

During the runs performed on Catalyst No. 6 in Example II and CatalystNo. 10 in Example IV, samples of the product oils were obtained andanalyzed for sulfur content by X-ray fluorescence analysis and nitrogencontent by coulometric analysis. As shown by the data in Table II, thesulfur and nitrogen contents of the feedstock were 2.37 wt.% and 0.079wt.%, respectively. In Table VII are reported the results of theanalyses performed on the samples of product oil obtained in theexperiments described in Examples II and IV. The data in Table VIIindicate that Catalysts Nos. 6 and 10 had substantial activity forhydrodenitrogenation and hydrodesulfurization.

                                      TABLE VII                                   __________________________________________________________________________         Temp.                                                                              Days into Run When                                                                       Sulfur in                                                                              Nitrogen in                                     Catalyst                                                                           °F.                                                                         Sample Taken                                                                             Product, ppmw                                                                          Product, ppmw                                   __________________________________________________________________________    No. 6                                                                              750  10          6       --                                              No. 10                                                                             730  10         93       2.2                                             No. 10                                                                             734  13         62       1.3                                             __________________________________________________________________________

EXAMPLE VIII

Zeolite LZ-10 is believed to be prepared by high temperature, steamcalcining the hydrothermally stable and ammonia-stable Zeolite Ycompositions described in U.S. Pat. No. 3,929,672, herein incorporatedby reference. One specific method by which LZ-10 may be prepared is asfollows:

A sample of air-dried ammonium exchanged Zeolite Y having a compositionexclusive of water of hydration:

    0.156Na.sub.2 O:0.849(NH.sub.4).sub.2 O:Al.sub.2 O.sub.3 :5.13SiO.sub.2

is tableted into 1/2 inch diameter slugs and charged to a Vycor tubeprovided with external heating means and having a 24 inch length and a2.5 inch diameter. The temperature of the charge is first raised to 600°C. in about 0.25 hours and then held at this temperature for one hour.During this 1.25 hour period, a pure steam atmosphere at 14.7 psiagenerated from demineralized water is passed upwardly through the chargeat a rate of 0.1 to 0.5 lbs/hr. Ammonia gas generated during the heatingdeammoniation of the zeolite is passed from the system continuously. Atthe termination of the heating period, the steam flow is stopped and thetemperature of the charge is lowered to ambient room temperature over aperiod of five minutes. The charge is removed from the Vycor tube, andthe sodium cation content of the steamed material is reduced to about0.25 weight percent (as Na₂ O) by ion exchange using an aqueous solutionof 30 weight percent ammonium chloride at reflux.

The low sodium material thus prepared is recharged to the Vycor tube andagain steamed, this time using pure steam at 14.7 psia and a temperatureof 800° C. for 4 hours. The product is then cooled to ambienttemperature and has the following typical characteristics: SurfaceArea=530 m² /gm, Adsorptive Capacity of water at 4.6 mm partial pressureand 25° C.=4.6 weight percent, and an ion exchange capacity equal to 4%of that of a sodium Y zeolite having a comparable SiO₂ :Al₂ O₃ ratio.(The comparable sodium Y zeolite to which LZ-10 zeolite is compared inthe specification and claims herein is a sodium Y zeolite havingessentially the same silica to alumina ratio as LZ-10 and having asodium to aluminum content such that the ratio of Na₂ O:Al₂ O₃ is equalto 1.0).

Although the invention has been described in conjunction with severalcomparative examples, many variations, modifications, and alternativesof the invention as described will be apparent to those skilled in theart. Accordingly, it is intended to embrace within the invention allsuch variations, modifications, and alternatives as fall within thespirit and scope of the appended claims.

I claim:
 1. A catalyst comprising at least one hydrogenation component,a crystalline aluminosilicate zeolite having catalytic activity forcracking hydrocarbons, and a dispersion of silica-alumina in a matrixconsisting essentially of alumina, wherein said catalyst comprisesparticles in the shape of a three-leaf clover.
 2. A catalyst as definedby claim 1 wherein said hydrogenation component is selected from thegroup consisting of Group VIII and Group VIB metals, their oxides andsulfides.
 3. A catalyst as defined by claim 1 wherein said hydrogenationcomponent is selected from the group consisting of platinum, paladium,cobalt, nickel, tungsten, molybdenum, their oxides, and their sulfides.4. A catalyst as defined by claim 1 wherein said crystallinealuminosilicate zeolite contains less than about 0.5 weight percentalkali metal components, calculated as alkali metal oxides.
 5. Acatalyst as defined by claim 1 wherein said zeolite is a Y zeolitehaving a silica-to-alumina mole ratio between 3.5 and 6.0, a surfacearea between 500 and 700 m² /gram, and an ion-exchange capacity when inthe sodium form less than 20 percent that of a sodium Y zeolite ofcomparable silica-to-alumina mole ratio.
 6. A catalyst as defined byclaim 1 wherein said matrix consists essentially of gamma alumina.
 7. Acatalyst as defined by claim 5 wherein said zeolite contains cationsselected from the group consisting of hydrogen ions and rare earthcations.
 8. A catalyst as defined by claim 1 wherein said zeolite isselected from the group consisting of zeolite Y, zeolite L, zeoliteOmega, zeolite X and mixtures thereof.
 9. A catalyst as defined by claim1 wherein said zeolite has a water absorption capacity at 4.6 mm watervapor partial pressure and 25° C. less than about 8 weight percent ofsaid zeolite.
 10. A catalyst as defined by claim 1 wherein said zeolitehas a unit cell size between about 24.25 and about 24.35 Angstroms. 11.A hydrocracking catalyst comprising at least one Group VIB metalcomponent and at least one Group VIII metal component, a crystallinealuminosilicate zeolite containing less than about 5.0 weight percent ofalkali metal components, calculated as the oxides thereof, and adispersion of silica-alumina in a matrix consisting essentially ofalumina, wherein said hydrocracking catalyst comprises particles in theshape of a three-leaf clover.
 12. A hydrocracking catalyst as defined byclaim 11 wherein said Group VIB metal component is selected from thegroup consisting of the oxides and sulfides of molybdenum and tungstenand said Group VIII metal component is selected from the groupconsisting of the oxides and sulfides of nickel and cobalt.
 13. Ahydrocracking catalyst as defined by claim 11 wherein said zeolitecontains one or more components selected from the group consisting ofhydrogen ions, hydrogen ion precurors and multivalent metal-containingcations.
 14. A hydrocracking catalyst as defined by claim 11 whereinsaid zeolite has at least 50 percent of its pore volume in pores ofdiameter greater than about 8 Angstroms.
 15. A hydrocracking catalyst asdefined by claim 11 wherein said zeolite is ion-exchanged to contain oneor more rare earth metal ions.
 16. A hydrocracking catalyst as definedby claim 11 wherein said zeolite has a water absorption capacity at 4.6mm water vapor partial pressure and 25° C. less than about 8 weightpercent of said zeolite.
 17. A hydrocracking catalyst as defined byclaim 11 wherein said zeolite contains less than about 0.5 weightpercent alkali metal components, calculated as alkali metal oxides. 18.A hydrocracking catalyst as defined by claim 11 wherein said matrixconsists essentially of gamma alumina.
 19. A hydrocracking catalyst asdefined by claim 18 wherein said dispersion of silica-alumina in amatrix consisting essentially of gamma alumina comprises between about20 weight percent and about 65 weight percent silica-alumina and saidsilica-alumina contains between about 50 weight percent and about 90weight percent silica.
 20. A catalyst as defined by claim 1 wherein saidzeolite comprises LZ-10 zeolite.
 21. A hydrocracking catalyst as definedby claim 11 wherein said zeolite comprises LZ-10 zeolite.